Experts find gene carrying big diabetes risk

January 16, 2006|By Nicholas Wade, the New York Times

Scientists have discovered a variant gene that leads to a sizable extra risk of Type 2 diabetes and is carried by more than a third of Americans.

The finding is being reported today in the journal Nature Genetics by researchers at Decode Genetics, a company in Reykjavik, Iceland, that specializes in finding the genetic roots of human diseases. Decode Genetics first found the variant gene -- one of many versions that exist in the human population -- in Icelanders and has now confirmed the finding in a Danish and an American population.

An immediate practical consequence of the discovery would be to develop a diagnostic test to identify people who carried the variant gene, said Kari Stefansson, chief executive of Decode. If people knew of their extra risk, they would have an incentive to stay thin and exercise, he said.

Diabetes, in which damaging amounts of sugar build up in the blood, with risk of blindness and loss of limbs, affects 20.8 million Americans, according to the Centers for Disease Control and Prevention.

Type 2 diabetes, the predominant form, is typically diagnosed in adults and adolescents, though it is creeping into younger age groups. The Type 2 kind accounts for up to 95 percent of all diagnosed cases, according to the CDC.

Because people carry two copies of every gene, one inherited from each parent, the risk conferred by the new gene depends on whether one or two copies of it have been inherited.

The estimated 38 percent of Americans who have inherited a single copy have a 45 percent greater risk of Type 2 than do unaffected members of the population. The estimated 7 percent who carry two copies are 141 percent more likely to develop the disease, said the Decode researchers, who were led by Struan F.A. Grant.

What scientists call the "population-attributable risk" of the new variant is 21 percent, which means that if all the variant genes in the population were erased, so would be 21 percent of diabetes cases.

The new variant identified by Decode was of a somewhat obscure gene that had not been suspected of having any involvement in diabetes. The gene, designated TCF7L2, controls the activity of other genes. Its role may include setting the level of a hormone that acts with insulin to control blood-sugar levels.